JPS60211774A - Manufacture of water repellent catalyst electrode - Google Patents

Abstract

PURPOSE:To obtain an electrolyte electrode having excellent electrolyte function and small electrical resistance by employing the structure that the catalyst element is directly held at the surface of graphite forming the surface layer or carbon fiber of electrode plate and between the layers and polytetrafluoroethylene is dispersely held between carbon fibers. CONSTITUTION:A carbon fiber paper or carbon fiber close which will be used as an electrode plate is impregnated with polytetrafluoroethylene. A donner type graphite interlayer compound is previously formed, in case the ion of catalyst element is positive, to the graphite at the surface of each carbon fiber of carbon fiber paper or carbon fiber close and a acceptor type graphice interlayer compound in case the ion of catalyst element is negative. Thereafter, when such compound is in contact with the ion of catalyst element, it can be held at the surface or interlayer or each graphite of carbon fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a water-repellent catalyst electrode, such as a water-repellent catalyst electrode suitable as an electrode for a fuel cell, and a method for producing the same.

[Background of the invention]

Catalytic electrodes used in fuel cells and the like are required to have excellent water repellency, that is, excellent gas diffusivity.

Conventionally, in order to manufacture a water-repellent catalyst electrode, a mixture of carbon powder and polytetrafluoroethylene (hereinafter abbreviated as PTFE), which is a water-repellent substance, is deposited on a porous carbon substrate (
For example, a method in which the catalyst element is applied to carbon fiber paper or carbon fiber cloth) and then supported on the coating layer by an impregnation method, or a method in which the catalyst element is supported on carbon powder by a deposition method and then PT is applied.
The method used was to add FE, knead it, and apply it to a porous carbon substrate.

However, the catalytic electrode manufactured by this method has a two-layer structure divided into a coating layer with a catalytic function (catalyst coating layer) and a carbon substrate which is a current collecting part, so the current collecting efficiency is low. The electrical conductivity of the catalyst coating layer is poor due to the addition of PTFE, so the overall electrical resistance loss is large, and some of the catalyst elements are surrounded by PTFE and deactivated. The reactants may not reach the catalyst coating layer sufficiently, the diffusion of the gas generated during the combination reaction will be significantly hindered by the catalyst coating layer, and the catalyst coating layer may crack or peel off from the carbon substrate. There were some issues, such as:

Furthermore, JP-A-57-124864 discloses that a graphite intercalation compound in which an acid is allowed to penetrate between graphite layers is used as the base of the catalyst layer, and the graphite intercalation compound is used in particles to which a catalyst is attached or particles mixed with catalyst particles. Then, mix this with a binder to make a paste and apply it to waterproofed carbon vapor, or make the paste into a sheet and attach it to waterproofed carbon vapor and pressurize it. , a heated gas diffusion electrode for fuel cells is disclosed. However, this electrode aims to increase the electrical conductivity of the carbon powder carrier by allowing acid to penetrate between the graphite layers, and its structure is a two-layer structure, so it cannot be said that it is a solution to the above problem. hard.

[Purpose of the invention]

In view of the above points, the present invention provides a water-repellent catalyst that has a single-layer structure in which the electrode substrate itself directly supports a catalyst, has low electrical resistance, has an effective catalytic action, and has good gas diffusivity. The object of the present invention is to provide an electrode and a method for manufacturing the same.

[Summary of the invention]

The water-repellent catalyst electrode of the present invention is made of an electrode plate made of carbon fiber paper or carbon fiber cloth, and a catalyst element is directly supported on the surface and between the graphite layers forming the surface layer of each carbon fiber of the electrode plate. , is characterized in that polytetrafluoroethylene is dispersed and supported between each of these carbon fibers.

The catalyst electrode of the present invention has a single-layer structure having the above-mentioned configuration, and each carbon fiber constituting the electrode plate supports the catalyst as described above, and also has a current collecting part. Since polytetrafluoroethylene, which is a water-repellent substance, is dispersed and supported between the carbon fibers, the catalytic action is effectively exhibited, and the electrical resistance is low. The gas generated by the operation of the electrodes has good diffusion, 6D, and there is little deactivation of the catalyst.

The above catalytic elements include Ru + R of group Ⅰ of the periodic table.
h r Pd r O@+ Ir + Pt * or Group 1b Ag + Au are suitable.

The water-repellent catalyst electrode of the present invention can be produced by the method of the present invention characterized by the following features. That is, the first step is to impregnate carbon fiber paper or carbon fiber cloth with Nipolytetrafluoroethylene, which will become the electrode plate, and the surface layer graphite of each carbon fiber of the carbon fiber paper or carbon fiber cloth that has undergone the above first step is impregnated with the carbon fibers described below. A second step of pre-generating a donor-type graphite intercalation compound when the ions of the catalyst component contacted in the third step are cations, and an acceptor-type graphite intercalation compound when the ions of the catalyst component are anions; and the second above
It can be produced by a method comprising a third step of bringing the carbon fiber paper or cloth that has undergone the process into contact with ions of the catalyst component.

As is well known, graphite has a stacked structure of planes (called layers) in which carbon atoms are arranged in a hexagonal network. Graphite intercalation compound is the gap between each layer of graphite (V
It is a compound formed by the invasion of other atoms and molecules into the gap (and der Waala gap). Graphite intercalation compound is
It is classified into two types, the donor type and the acceptor type, depending on the atoms, molecules, etc. that invade the glabella of graphite. Donner's graphite intercalation compound is a graphite intercalation compound in which electrons are transferred from penetrating atoms, molecules, etc. to graphite. The acceptor type graphite intercalation compound is a graphite intercalation compound in which electrons are transferred from the graphite to atoms, molecules, etc. that have entered.

Examples of donor-type intercalation compounds include intercalation compounds of graphite and alkali metals, and intercalation compounds of graphite and alkaline earth metals. A representative example of the acceptor type intercalation compound is an intercalation compound of graphite and Pronsted acid.

In the production method of the present invention, it is necessary that the graphite intercalation compound that is generated in advance in the second step matches the polarity of the ions of the catalyst component that is to be brought into contact with it in the third step, that is, When the ions of the catalyst component are positive ions, the graphite intercalation compound is a donor type intercalation compound, and when the ions of the catalyst component are negative ions, the graphite intercalation compound is an acceptor type intercalation compound. It is necessary that When carbon fiber paper or carbon fiber cloth on which such a graphite intercalation compound has been formed in advance is brought into contact with matched positive or negative catalyst component ions, the catalyst element penetrates between the graphite layers due to ion exchange, or A reaction occurs in which the ionized catalyst component is reduced by the electrons of the compound and the catalyst element is supported on the graphite surface, and the catalyst element can be supported on the graphite surface and between the eyebrows of each carbon fiber. can.

Since the graphite intercalation compound is generally unstable in the atmosphere, the graphite intercalation compound and ions of the catalyst component may be mixed in an inert gas or in a liquid such as an organic liquid that does not substantially react with the graphite intercalation compound. It is desirable to contact the

Example 1 5 μ of PTF per 1 square α of carbon fiber paper with a thickness of 0.8
After impregnating E, this carbon fiber paper and metallic potassium were packed in a glass tube at a weight ratio of 2:1, vacuum sealed at a pressure of aklOPi, and then heat treated at a temperature of 250°C for 2 hours. A golden first stage graphite-potassium intercalation compound was formed. Here, the first stage graphite intercalation compound is a term for a graphite intercalation compound in which another substance (potassium in this example) is present between all layers of graphite.

Thereafter, the carbon fiber paper on which the graphite intercalation compound was formed was immersed in a tetrahydrofuran (C4H80) solution in which chloroplatinic acid (H2PtC46.6H20) was dissolved.

In the carbon fiber paper treated as described above, it was confirmed by X-ray diffraction measurement that platinum as a catalyst was supported on the surface of graphite in the surface layer of each carbon fiber and between the eyebrows. Also, P.T.
It was confirmed that FE was separated and scattered among the carbon fibers. This carbon fiber paper was soaked in water for 1000 hours,
It was confirmed that water repellency was maintained.

Example 2 Carbon fiber paper with a thickness of 1.2 m impregnated with 9 ml of polytetrafluoroethylene per square centimeter and rubidium metal were placed separately at both ends of a glass tube, and 10-2P
It was vacuum sealed with a. This glass tube was placed in an electric furnace whose temperature could be controlled at two points, and heat treated at 400° C. on the carbon fiber paper side and 208° C. on the metal rubidium side for 4 hours to form a deep blue second stage graphite rubidium intercalation compound. Here, the second stage graphite intercalation compound is a name for a graphite intercalation compound in which another substance (rubidium in this example) is inserted between every other glabella of graphite. Thereafter, the carbon fiber paper on which the graphite intercalation compound was formed was immersed in a tetrahydrofuran (C4H80) solution in which potassium chloroplatinate (K2PtCl4) was dissolved.

The carbon fiber paper treated as described above has platinum as a catalyst supported on the surface and between the graphite layers of each carbon fiber, and PTFE is supported dispersedly between the carbon fibers. Confirmed by X-ray diffraction measurement, 1M observation, and EDx analysis. The platinum particle size on the surface was 35X. Further, this carbon-# miscellaneous paper did not lose its water repellency even after being immersed in water for 1000 hours.

Example 3 Carbon fiber cloth was impregnated with 12 to 12 polytetrafluoroethylene per square centimeter. This carbon fiber paper woven fabric and metallic potassium were placed in a glass tube at a weight ratio of 6:1.
After vacuum sealing at 100-3P pressure, 3
A deep blue second stage graphite-potassium intercalation compound was formed by heat treatment for a period of time. Thereafter, the carbon fiber cloth with the graphite intercalation compound formed thereon was treated with chloroauric acid (HzAuCZ).
) and ruthenium chloride (RuC13XJ (20)) were dissolved in a tetrahydrofuran solution.The water content of the tetrahydrofuran solution was 21 pprn.

In the carbon fiber cloth treated in this way, gold and ruthenium as catalysts are supported on the surface and between the graphite layers of each carbon fiber, and PTFE is separated and scattered between the carbon fibers. Linear diffraction measurement, SEM observation, ED
X analysis confirmed that the water repellency was not lost even after this carbon fiber cloth was immersed in water for 1000 hours.

〔Effect of the invention〕

According to the present invention, the individual carbon fibers of the carbon fiber paper or carbon fiber cloth constituting the electrode plate form a current collecting part and at the same time form a catalyst part carrying a catalytic element between the graphite layers and on the surface thereof. Therefore, a catalytic electrode having both good catalytic function and low electrical resistance can be obtained. Moreover, carbon fiber paper and carbon fiber cloth are porous, and the water-repellent substance is separated from the catalyst and dispersed and supported between the carbon fibers, so they have good water repellency and are not only water-repellent substances. There is no deactivation of the catalyst due to being surrounded, and the penetration of chemical reactants into the electrode and contact with the catalyst are good, so the catalytic action works effectively and the diffusivity of the gas generated at one electrode is improved. do.

Furthermore, since the water-repellent catalyst electrode of the present invention has a single layer structure,
Needless to say, there is no problem of cracking or peeling of the coating layer or the adhesive layer, which is the case with conventional electrodes having a two-layer structure consisting of a substrate and a coating or adhesive layer thereon.

Claims (1)

[Scope of Claims] 1. An electrode plate made of carbon fiber paper or carbon fiber cloth, in which a catalytic element is directly supported on the surface and between the graphite layers forming the surface layer of each carbon fiber of the electrode plate, A water-repellent catalyst electrode characterized in that polytetrafluoroethylene is dispersed and supported between each of these carbon fibers. 2. The catalytic element is Ru + Rh from Group Ⅰ of the periodic table *
Pd + Os * Ir + Pt or Group 1b Ag
, The water-repellent catalyst electrode according to claim 1, which is made of Au. 3. The first step of impregnating polytetrafluoroethylene into carbon fiber paper or carbon fiber cloth that will become the electrode plate, the first step described above.
When the ions of the catalyst component to be brought into contact with the surface layer graphite of each carbon fiber of the carbon fiber paper or carbon fiber cloth that has undergone the process in the third step described below are cations, a donor type graphite intercalation compound is added to the surface layer graphite of each carbon fiber of the carbon fiber paper or carbon fiber cloth that has undergone the process. When the ions are anions, the second step is to generate an acceptor graphite intercalation compound in advance, and the third step is to contact the carbon fiber paper or carbon fiber cloth that has undergone the second step with the ions of the catalyst component. A method for producing a water-repellent catalyst electrode characterized by: 4. The repellent according to claim 3, wherein the donor type graphite intercalation compound is an alkali metal or alkaline earth metal graphite intercalation compound, and the acceptor type graphite intercalation compound is a Pronsted acid graphite intercalation compound. A method for producing an aqueous catalyst electrode.